In the model, a proportion \(I_0\)  of the population were initially infectious, and the rest of the population were susceptible. This resulted in four parameters to be estimated (\(\beta \) , \(\gamma \) , \(r\) , and \(I_0\) ). Parameter estimation was performed using Markov chain Monte Carlo (MCMC). As the games often placed a 24 hour time limit on individuals to complete the activity [1]}, [2]}, a gamma distribution was used as the prior for the mean infectious period, with \(\mu =1\)  day and \(\sigma ^2=0.1\) . The posterior distribution was obtained from sampling over 40,000 MCMC iterations, after a burn-in period of 10,000 iterations (Figures S1–S4). The model was implemented in R version 3.2.3 [3]}, with ODEs solved numerically using the ode45 method in the deSolve package [4]}.
